1. Field of the Invention
The invention relates to a magnetic-tape apparatus comprising at least two manually operable push-buttons for selecting modes of operation of the apparatus, each button being associated with a stop defining the mode of operation selected by actuation of the button. A servo-mechanism which is put into operation by actuating a button positions at least one apparatus part in conformity with the selected mode.
The mechanism comprises a servo disc which can be driven by a motor and which can be made to rotate upon actuation of a button, a first eccentric means arranged on the servo disc, a drive member movable by said eccentric means, and an actuating member which is movable by the drive member to position the apparatus part. The actuating member can be set to different operating positions, defined by the stops associated with the buttons, by a control device which can be put into operation upon actuation of a button.
The control device comprises a second eccentric means which can be driven by the motor, and at least one scanning element for scanning the stops. The scanning element cooperates with the second eccentric means and with the actuating member, and can be released by the second eccentric means to scan the stops. In order to scan a stop after the scanning element has been released, it can be positioned against the stop which defines the selected mode under the influence of at least one spring, actuation of a button firstly causing the second eccentric means to release the scanning element in order to scan the stops, so that the spring urges the scanning element against the stop which defines the selected mode and the scanning element moves the actuating member to the position defined by the stop corresponding to the selected mode. Then the first eccentric means moves the drive member, which drive member moves the actuating member, and the actuating member positions the apparatus part.
2. Description of the Prior Art
Such apparatus is disclosed in, for example, German Offenlegungsschrift No. 28 50 239 to which U.S. Pat. No. 4,225,894 corresponds. In the known apparatus the control device for controlling the positions of the actuating member comprises a control disc which can be driven by a separate motor and which carries the second eccentric means which cooperates with the scanning element. Such a separate control disc results in additional cost, demands additional space and also complicates assembly of the apparatus, because the position of the control disc and the servo disc relative to each other must be defined accurately to ensure a correct coordination of the movements initiated by the two discs via the eccentric means.
Further, from German Offenlegungsschrift No. 19 46 150 it is known to provide a plurality of eccentric means on a radial surface of a servo disc in order to obtain coordinated movements of apparatus parts. However, these eccentric means are superimposed relative to the radial surface, so that the thickness of the servo disc and hence the height of the apparatus become comparatively large.